One of the most important challenges of our century concerns reduction of the negative effects of human activities on the Environment. The development of new technologies thus owes integrate a responsible approach of both environmental and societal management to build a sustainable industry, in particular in the chemical industries.
Thus, in the latest century was born the concept of “green chemistry”, namely a chemistry worried of implementing principles of reduction or limited generation of harmful substances for the Environment since its sources.
For instance, in pharmaceutical and chemical industry, nitrogen heterocyclic compounds, mainly N-heterocyclic carbenes (NHC), are commonly used in many applications such as ligands for organometallics catalysts, organic catalyst, material and drug syntheses, therapeutics or electrochemistry. However, these high value-added products have been prepared until now, by energy-consuming processes that use reagents with strong negative environmental impacts. Furthermore, their handling is still sensitive: the used conditions of NHC synthesis lead to highly explosive atmosphere and finally, to high professional risks. Consequently, it is necessary to develop both eco-friendly and safe processes in this chemical field.
Currently, a large majority of N-heterocyclic carbenes are synthesized from their corresponding imidazolium salts by deprotonation with a strong base (n-BuLi, tBuOK, NaH), which usually requires special conditions (low temperature, inert atmosphere; Arduengo, A. J., Acc. Chem. Res., 1999, 32, p 913). Numerous works are devoted to the synthesis of an intermediate stable masked carbenes allowing regenerating in situ free carbenes by thermal activation. Among these compounds, imidazolium 2-carboxylate compound is particularly interesting in that it allows spontaneous carbon dioxide delivery.
Until now, two chemicals pathways have been reported to prepare imidazolium 2-carboxylate. The first one (method A) consists of deprotonation of imidazolium salt compound at low temperature and under inert atmosphere in order to provide a free intermediate carbene which then, will react by contacting itself with a solution comprising carbon dioxide (Kuhn, N. et al. Naturforsch 1999, 54b, 427):

During this reaction, a very reactive carbene is provided, constraining the experimenter to work at cryogenic temperatures for avoiding any pyrophoric risk.
The second (method B) refers to a <<one-pot>> reaction of both N-methylation and C-carboxylation of N-monosubstituted imidazole precursor using dimethylcarbonate (DMC) as a reagent (Holbrey, J. et al. Chem. Commun. 2003, 28):

Contrary to the first method, this latest chemical way requires high temperature and pressure conditions that limit methylation (with DMC) reaction on the remaining unsubstituted-N atom and needs specific experimental material.
The aim is thus to provide imidazolium carboxylate compounds by a green process easy to implement, safe and allowing having products without toxic subproducts.
Surprisingly, the Applicant has discovered a process and a new electrochemical device for preparation of imidazolium 2-carboxylate overcoming the drawbacks previously described. Especially, the Applicant has further discovered a method for preparation of new imidazolium salts, particularly imidazolium hydrogenooxalate salts from bio-based reagents, useful for providing bio-sourced imidazolium 2-carboxylate compounds by a more eco-friendly electrochemical way.